This invention relates to arrangements by which connecting pieces are fixed to products of composite material to form a joint between them.
Generally, composite material is referred to herein as a combination of a binding material matrix and reinforcing fiber material extending through the matrix. For example, the binding material matrix can comprise epoxy or polyester resins, or certain thermoplastic materials. The reinforcing fiber materials can, for example, comprise fiberglass or fibers of carbon, polyetheylene, etc.
A typical application for the present invention is in connection with pipes manufactured of composite material of the type used in offshore installations. Such pipes are of relatively low weight and are therefore particularly suited to replace conventional metallic pipes typically formed of stainless steel. A problem, however, in replacing metallic pipes with pipes formed of composite material is in the technique by which the pipes are joined to each other. More particularly, where the connection between two pipes is subject to high tensile strains, conventional technology does not provide an adequate solution.
The most commonly used technique for joining two products formed of composite material is by gluing. Gluing, however, has the drawback of providing insufficient shear strength.
Another conventional technique for joining two composite material products is a mechanical joint of the type described, for example, in U.S. Pat. No. 4,549,919. However, such mechanical joints require an additional connecting piece which increases the size and weight of the joint which is undesireable.
A third conventional technique used in joining a pair of products of composite material comprises a superposed lamination. A drawback of this technique, however, is that an additional manufacturing step is required which involves an increased amount of work. Further, the strength of the connection is relatively low due to the reduced area of the joint. Moreover, formation of such a connection requires additional composite material.